Preparation and Characterization of Mixed‐Valent Nickel Oxide/Nickel Hexacyanoferrate Hybrid Films and Their Electrocatalytic Properties

Polynuclear mixed‐valent nickel oxide and nickel hexacyanoferrate hybrid film was prepared on glassy carbon electrode by multiple scan cyclic voltammetry. The film growth was monitored using electrochemical quartz crystal microbalance (EQCM). The cyclic voltammogram of the nickel hexacyanoferrate film is characterized by single redox couple whereas nickel oxide/nickel hexacyanoferrate hybrid film exhibits two redox couples. Cyclic voltammetric features suggest that the charge transfer process in both films resembles that of surface‐confined redox species. In stronger basic solution (pH ≥9), nickel hexacyanoferrate film was gradually converted into nickel oxide film during potentiodynamic cycling. The peak potential of nickel oxide redox couple moved into more negative side with increasing pH of contacting solution whereas the peak potential of nickel hexacyanoferrate redox couple remains the same. Electrocatalytic behavior of hybrid film coated electrodes toward ascorbic acid, hydrazine and hydroxylamine was investigated using cyclic voltammetry technique. Analytical application of nickel oxide/nickel hexacyanoferrate hybrid film electrode was tested in amperometry and flow injection analysis.     

In search of new resonance structures in dissociative photoionization of H2

We present a theoretical study of dissociative photoionization of H₂ via the ¹Π_u symmetry in the photon energy range 30–43 eV. Our results explain the various peaks observed in the experiments below 40 eV and illustrate, in particular, the important role of the ²Π_u(2pπ_u) ionization threshold. At higher photon energies, they suggest the existence of new resonance structures that may be associated with doubly excited states of H₂ lying above the third and fourth ionization thresholds (the Q₃ and Q₄ resonance series). From the calculated resonance parameters, we conclude that the dominant mechanism at high photon energies should involve the Q₄ (and probably higher) doubly excited states of H₂. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2002     

Tweezer分子的合成和对有机阴离子的配位效应

本文报道新的Ｔｗｅｅｚｅｒ（１）的合成，用＾１ＨＮＭＲ研究了新的Ｔｗｅｅｚｅｒ分子和对硝基苯甲酸盐的配位效应，结果表明它兴通过氢键，静电引力和芳环夹心堆叠作用而自动缔合。     

Polyparametric modification equation for estimating thermodynamic properties of energetic nitro compounds

Calculation methods, based on hybrid density-functional theory with the basis sets of B3LYP/ 6-311+G (2d, p)//B3LYP/6-31G(d, p)and B3LYP/6-31+G(d)//B3LYP/6-31G(d, p), were applied to determine the thermodynamic characteristics of various energetic nitro compounds. A parametric modification equation and the least-squares approach were used to identify 21 of the energetic research compounds. The atomization energies of these 21 compounds have an average relative error of 0.21–0.25% of the experimental values. The enthalpy (H _f) and the Gibbs energy (G _f) of formation have mean absolute errors of 10.8–11.4 kJ/ mol (2.6–2.7 kcal/mol) and 10.0–10.3 kJ/mol (2.4 kcal/ mol), respectively. The enthalpy and the Gibbs energy of formation obtained exceed those in the literature obtained by semiempirical calculations. The calibrated least-squares parameters and parametric equations were used to predict H _f and G _f for the five newly developed energetic nitro compounds for further applications.Acknowledgements. The authors would like to thank the National Science Council of the Republic of China for financial support of this work under grant no. NSC-91-2113-M-014-003. The National Center for High-Performance Computing providing the computation facility is also acknowledged.     

Markov processes in single molecule fluorescence

This article examines the current status of Markov processes in single molecule fluorescence. For molecular dynamics to be described by a Markov process, the Markov process must include all states involved in the dynamics and the first-passage time (FPT) distributions out of those states must be describable by a simple exponential law. The observation of non-exponential FPT distributions or other evidence of non-Markovian dynamics is common in single molecule studies and offers an opportunity to expand the Markov model to include new dynamics or states that improve understanding of the system.     

基于Cz-DPP不对称D-A结构新型有机小分子光伏材料的合成与性质

本文设计合成了一系列以咔唑(CZ)和吡咯并吡咯二酮(DPP)为基本结构单元的D-A结构的新型小分子材料,并对其进行了一系列的性能表征.合成的材料以咔唑作为给电子单元,吡咯并吡咯二酮作为吸电子单元,采用三键作为π桥,并引入4-氟苯基、4-氰基苯基和4-甲氧基苯基作为末端取代基团对材料进行修饰.其中材料CZBTDPPF和CZBTDPPO因分别具有1.85和1.79 eV的较窄带隙而分别获得了相对较高的的光电转化效率(1.97%和1.91%).由此可见,引入4-氟苯基和4-甲氧基苯基作为末端取代基团对于延长材料共轭结构、拓宽材料吸收从而实现材料光伏性能的提升具有重要的作用.     

Synthesis of well-defined polymers with protected silanol groups by atom transfer radical polymerization and their use for the fabrication of polymeric nanoparticles

Copper-mediated atom transfer radical polymerization (ATRP) of a protected silanol group-holding methacrylate, methacryloxypropyltrimethoxysilane (MOPS), was investigated. In a dry condition using carefully distilled solvent and monomer, the polymerization proceeded in a living fashion providing a low-polydispersity polymer with a predicted molecular weight. The ATRP in conjunction with the sequential monomer addition of methyl methacrylate (MMA) and MOPS afforded a block copolymer of the type PMMA-b-poly(MMA-r-MOPS). The heat treatment of a solution of the block copolymer in the presence of a catalytic amount of ammonia gave a polymeric core-shell nanoparticle with a shell of PMMA moieties and a core of the poly(MMA-r-MOPS) blocks cross-linked via the condensation of the trimethoxysilane groups of the MOPS moieties.     

Accurate Gaussian basis sets for the H2O molecule generated with the molecular improved generator coordinate Hartree–Fock method

The molecular improved generator coordinate Hartree–Fock (MIGCHF) method is used to generate accurate basis sets of primitive Gaussian-type functions for the H₂O molecule. Sequences of increasing size atom centered basis sets are employed to explore the accuracy that can be achieved with this method. Using the O(24s14p8d5f2g1h);H(22s9p5d2f1g) basis set, the HF and second-order electron correlation energies of the H₂O ground state at the experimental geometry are computed as −76.0674680 and −0.3491935 hartree, respectively. The HF energy is in error by 20 μhartree and the second-order correlation energy corresponds to 96.5% of an estimate of the limiting value. The relevance of the present calculations is to show the accuracy that can be achieved in studies of small polyatomic molecules with the MIGCHF method.     

A two-dimensional infrared correlation spectroscopic study on the thermal degradation of poly(2-hydroxyethyl acrylate)-co-methyl methacrylate/SiO2 nanohybrids

Two-dimensional infrared (2D IR) correlation spectroscopy was applied to study the structural changes occurring in the decomposition of PHEA-co-MMA/SiO₂. Complicated absorption spectral changes were observed in the heating process. 2D IR analysis indicates that during heating, covalent bonds, (Si-O-C), between the polymer and the inorganic moiety were formed, which was the main factor in the improvement in thermal properties of the hybrids such as the decomposition temperatures (T_d). The thermal stability of the hybrids was also studied by solid-state ²⁹Si MAS NMR spectroscopy and TGA tests. Their results complemented each other well.     

Recent progress in two-photon small molecule fluorescent probes for enzymes

This review aims to provide a summary of the progress in TP small molecule fluorescent probes for enzymes in recent years and displays the main fluorescent mechanisms that have been applied to design probes.